a. Field of the Invention
The present invention relates generally to catheters and catheter navigation systems.
b. Background Art
Recent years have witnessed an expanding need for percutaneous, endocardium-based cardiac interventions, including ablation, injection, and device deployment. These interventions are generally not focal, but rather involve a broad region of endocardial anatomy. This anatomy is complex topographically, as well as motile. Current modalities for real-time intraoperative endocardial imagining and navigation are highly inaccurate, which has been the cause of procedure inefficiency and complications.
One such procedure is catheter ablation of the left atrial endocardium. This procedure is performed in an attempt to cure atrial fibrillation, a common heart rhythm disorder. The left atrium, as noted above, has a complex topography and motility. At present, the ablation procedure is performed by attempting to “register” preoperative four-dimensional imaging data (derived from computed tomography) and with two-dimensional intraoperative imaging data derived from intracardiac echocardiography and fluoroscopy). This is laborious, highly operator-dependent (which prohibits dissemination) and inaccurate.
Typically, two major sensor systems are used during ablation procedures to assist clinicians to navigate catheters: (1) a magnetic tracking system, which can track the 3D position of the catheter tip and yaw, pitch, and roll of the catheter; and (2) intracardiac ultrasound imaging sensor, which can generate a 2D section view in real time inside the heart chambers. Sometimes X-ray pictures are used as well. Apparently, all these sensors are used independently. That is, an ultrasound-imaging sensor is used to see visually if the ablation catheter is touching the hard wall and the magnetic tracking system is used to visualize the ablation sites without any relative position information to the heart.
In order to visualize the catheter's position relative to the heart, the registration must be done between the magnetic tracking system and a heart model derived from a CT scan or an MRI captured prior to surgery. Some similar 3D registration systems are available for surgery of rigid body parts, such as hipbone surgery. Software such as BioSense Webster's CARTOMERGE can be used to do the 3D registration between the magnetic tracking system and the 3D heart model from the CT scan. These systems basically do the registration based on 3D shape. In order to do the registration, a set of registration points needs to be captured. That is, clinicians need to move a probe or catheter whose position is tracked to touch the surface of the bones or heart wall and record all those positions.
These systems work well with rigid or almost rigid human body parts, such as bones or brain. In contrast, the shape of the human heart changes dramatically through every cardiac cycle. Also, the respiration or breath of a person can also change the pressure of the person's lung and eventually change the shape of the person's heart.
Relevant prior art includes U.S. Pat. No. 6,556,695, which discloses a method and system for high resolution medical images in real-time to assist physicians in the performance of medical procedures. The disclosed method includes: acquiring image data of the subject anatomy and reconstructing an image which is a high resolution model of the subject anatomy; performing a medical procedure in which the subject anatomy is imaged in real-time by acquiring low resolution images at a high frame rate; registering the high resolution model of the subject anatomy with each acquired low resolution image; and displaying to the physician in real-time images of the registered high resolution model of the anatomy. The high-resolution model may be a 2D or 3D image of static anatomy, or it may be a 4D model in which the fourth dimension depicts changes in the anatomy as a function of time, cardiac phase, respiratory phase, or the like. The creation of this model is performed using a high resolution imaging modality and it may be done prior to performing the medical procedure. The registration of the high resolution model is performed in real-time and includes a 2D or 3D spatial orientation as well as a registration in time or phase when the model depicts changing anatomy.